Coping with Extraneous Water in Sewerage Systems

Abstract

The presence of extraneous water is a common deficiency for the sewerage systems nowadays. It may have different origin: surface or underground water, or water due to leaking water supply pipes. The amount depends mostly on the age and the level of maintenance of the sewer network. Defects of sewer pipes that allow infiltration may also allow exfiltration of sewer water into the soil and thus jeopardise the underground water quality. Both phenomena affect negatively the operation and maintenance of the sewer system and often result in higher energy demand or ineffective performance of the treatment facilities. This chapter presents a simplified 5 steps methodology for estimating the presence and amount of extraneous water in sewerage systems, for which a WWTP has not been built yet. Other advantage is that the methodology does not require significant investments or extensive period of investigation. Its application is described in details for two case studies alerting the attention on the key factors that should be taken into account. Although the methodology carries some uncertainty the results obtained can indicate major problems and can help engineers to select technically and economically feasible solutions for rehabilitation of the municipal water supply and sewerage infrastructure.